Rotary screen printing cylinders

ABSTRACT

The invention relates to the engraving of rotary screen cylinders for use in printing fabrics and the like. The required design is first engraved as a pattern of permeable and impermeable areas on a flat screen matrix. This matrix is mounted in contact with the cylinder and while it is moved in its plane and the cylinder rotates a blocking medium is forced through the matrix on to the cylinder to form the required pattern thereon.

United States Patent [72] Inventor Almerindo Jamie De Oliveira Barros 1,886,846 1 1/1932 Taylor 101/121 Lisbon, Portugal 2,498,917 2/1950 Gattuso 101/124 [21] Appl. No. 698,500 2,796,164 6/1957 Hakogi 101/40X [22] Filed Jan. 17, 1968 3,081,698 3/1963 Childress et a1. 101/114X [45] Patented Feb. 23,1971 3,302,561 2/1967 Edwards 101/38 [73] Assignee Aljaba Limited 3,369,484 2/1968 Cross 101/38 Manchester, Lancashire, England l 32 1 Priority Jan. 1967 v Pru zary Examiner Robert E. Pulfrey B AssrstantExammer-Alan E. Kopecki ;3; Attorney-Wenderoth, Lind & Ponack [54] ROTARY SCREEN PRINTING CYLINDERS 5 Claims, 3 Drawing Figs. [52] US. Cl 101/38, 101/124,101/126 [51] Int. Cl 134" 17/08, ABSTRACT; The invention lates to the engraving of rotary 841127/00 screen cylinders for use in printing fabrics and the like. The [50] Fleld of Search lOl/l 14, i d design i fi t engraved as a pattern f permeable and 116121v122124,129,126,35,3840 impermeable areas on a flat screen matrix. This matrix is [56] R f C1 d mounted in contact with the cylinder and while it is moved in e erences I e its plane and the cylinder rotates a blocking medium is forced UNITED STATES PATENTS through the matrix on to the cylinder to form the required pat- 689,189 12/1901 Hornung 101/36 tern thereon.

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' SHEET 3 UF 3 I mm :mm: comm as ouvsnu BAIRHS MMMJMHHAL PM ROTARY SCREEN PRINTING CYLINDERS This invention relates to rotary screen printing cylinders and is concerned with a method of engraving such cylinders, that is, forming such cylinders with a pattern of permeable and impermeable areas corresponding to the design to be printed.

According to one aspect of this invention there is provided a method of engraving a rotary screen cylinder with the negative of a pattern to be printed on textiles or the like, comprising the steps of mounting the rotary screen cylinder for rotation; mounting a flat screen matrix, carrying a positive engraving of said pattern, for movement in a plane tangential to said cylinder; applying a blocking medium to the patterned zone of said matrix and drawing the patterned zone of said matrix over the cylinder while applying a preadjusted nipping pressure to the matrix and cylinder at the position at which they interengage, so as to fill the blocking medium through the matrix and into the interstices of the cylinder and form therein a negative engraving of the pattern on the matrix.

The blocking medium used is one which is capable of standing up to the strains sustained by the pattern on the rotary screen cylinder during the printing operation. In this specification the term lblocking medium" is intended to include within its scope lacquers, enamels, paints, resins or varnishes, for example those based on polyurethane, polyvinyl chloride or epoxy resins, which may be used for engraving stencil printing screens for the textile industry.

According to another aspect of the invention there is provided apparatus for engraving a rotary screen cylinder with the negative of a pattern to be printed on textiles or the like, comprising means for mounting the rotary screen cylinder for rotation; means for mounting a flat screen matrix, carrying a positive engraving of said pattern, for movement tangentially to said cylinder and so as to rotate said cylinder; means for applying nipping pressure to the matrix and cylinder at the position at which they interengage, and means for preadjusting said nipping pressure for causing blocking medium applied to said matrix to be filled through the matrix and into the interstices of the cylinder, when the matrix is moved and the cylinder rotated.

The blocking medium is preferably applied on to the surface of the rotary screen cylinder through the matrix by squeegee means and preferably the rotary screen cylinder is mounted with an internal supporting roller located within the rotary screen cylinder and with its axis in a plane containing the axis of the rotary screen cylinder and the axis of the squeegee means. This supporting roller is preferably adjustably mounted relative to the means supporting the rotary screen cylinder. Similarly the squeegee means can be moved into heavier or lighter contact with the matrix as desired.

The matrix is preferably pulled through the nip between the rotary screen cylinder and the squeegee means so that the rotary screen cylinder rolls along one side, normally the underside, ofthe matrix.

An embodiment of the invention will now be described by way ofexample, with reference to the accompanying drawings in which:

FIG. 1 is a perspective view of apparatus for engraving a design on to a rotary screen cylinder;

FIG. 2 is a longitudinal section on the line 2-2 of FIG. 1 with the matrix and the rotary screen cylinder omitted for clarity; and

FIG. 3 is a section on the line 3-3 of FIG. 1.

The apparatus of the invention comprises a main framework and a subassembly for carrying the rotary screen cylinder. The subassembly is releasably mounted in fixed relation on the main framework. Slidably mounted on the main framework is a rectangular frame for carrying the flat matrix which is to be used for engraving the rotary screen cylinder which may be over 80 inches long. In use, lacquer will be passed through the matrix to engrave the rotary screen cylinder.

Referring now to the drawings, and in particular to FIG. 1, the main framework comprises two frames 14 and 15. Each frame comprises a channel-shaped base member 16 and two side uprights 17 which are connected by an upper crossmember 18. The rear side uprights 17 extend beyond the upper crossmember l8 and support the rear end of an upper longitudinally extending member 19, the forward end of which is supported by a bracket 21. An intermediate vertical member 22 extends upwardly from the base member 16 through the upper member 18 and the top member 19 for a purpose that will be described. A cross brace 23 extends between the intermediate members 22 of each frame. This cross brace serves to keep the two frames 14 and 15 correctly located. The bracket 21 on the frame 14 carries an electric motor 24 which drives a small pulley 25 through a reduction gearbox 26 for a purpose that will be described. A cord 27 extends from the pulley 25 around an idler pulley 28 carried on an extension bracket 29 that projects beyond the end of the frame 14.

The upper members 19 are each formed with a guide track 31. A pair of crossmembers 32 each provided with a roller 33 at each end and a pair of longitudinal members 34 constitute a rectangular frame which is movable along the members 19 with the rollers 33 engaging the guide tracks 31. The matrix 35 stretched on its carrying frame 35a is releasably received by this frame, the matrix frame resting on flange parts 320 secured on the cross members 32. The matrix frame 35a also has a pair of spaced slotted lugs (not shown) located on one transverse side thereof. A pair of corresponding spiked rods are provided on the moving frame. By engaging the rods in the slots of the lugs, the matrix frame 35a can be accurately located on the moving frame. The matrix 35 is formed by engraving the required design by the use of conventional method on to a flat screen made of nylon, metallic mesh or other appropriate material. The engraving on the matrix is the positive of the design that is to be reproduced on the fabric to be printed. The moving frame has a central lug 32b on the front transverse member 32 and the cord 27 is attached to this lug 32b.

The intermediate vertical members 22 are provided at their upper ends, which project beyond the top members 19 with a rectangular box framework 36 in which is received the upwardly cranked ends 37 of a transverse support member 38. Each end 37 rotatably receives the end of a calibrated threaded member 39 and holds this latter end against relative axial movement. The member 39 threadedly engages a nut member 41 supported by the frame 36 and is rotatable by a handle 42.

Carried by the transverse support member 38 is a rubber covered or metallic squeegee 43 which may be cylindrical as shown or formed as a blade. This squeegee 43 has end arbors carried respectively by two box frames 44 which surround the crossmember 38 so as to be movable both axially and up and down relative to the crossmember 38. Each box frame 44 incorporates an adjustable screw operable by a handle 45 so as to be able to limit slightly the amount of movement of the box frame 44 up or down relative to the crossmember 38 so that the nipping pressure applied by the squeegee 43 in cooperation with the roller 56 (referred to below) may be manually adjusted. A weight box 46 is located above the center portion of the squeegee 43. This weight box 46 is provided with a pair of box frames 47 which extend from the weight box 46, surround the transverse support member 38, and are provided with cupped feet 48 that rest upon the squeegee 43. By choosing the weights that are inserted in the weight box 46 one can ensure that the correct pressure is applied by the squeegee.

The screen-carrying subassembly 50 comprises a crossbar 51 which spans the frames 14 and 15 below the squeegee 43 with its ends projecting between the members 18 and 19. The ends of the crossbar 51 have recesses to enable them to be located on a pin, which is an extension of adjusting screw 53, so that the crossbar 51 can be raised or lowered as required. Additionally the locating pins at the end of screw 53 ensure that subassembly 50 is kept in alignment to the main frame. A clamp 52 can be set so as accurately to maintain the height to which crossbar 51 is raised. Handles 54 project from the ends of the crossbar 51 to facilitate manhandling the subassembly 50 when moving this to its position on the main frame and to and from an auxiliary supporting frame (not shown) and when placing a rotary screen cylinder 12 on to the subassembly.

A pair of collars 55 (only one shown) are rotatably mounted on the crossbar 51 and are spaced so as to be able to fit into the ends of the rotary screen cylinder 12 to carry the latter. This rotary screen cylinder 12 can conveniently be a two-ply cylinder as described in British Patent Specification No. 1,050,649. A supporting roller 56 of slightly less axial length than the cylinder 12 is carried by the cross bar 51 with its axis parallel to and directly above the axis of the collars 55. The supporting roller 56 is located so that its surface runs along the inner surface of the cylinder 12 to support the cylinder 12. When the subassembly 50 is correctly adjusted, the roller 56 is located directly below and in alignment with the squeegee 43 and cooperates therewith to provide the requisite nipping pressure on the matrix and cylinder. The supporting roller 56 has end trunnions 57 that are guided in lugs 58 on the crossbar 51, which lugs 58 allow free vertical movement of the supporting roller 56. A number of adjusting rollers 59, usually three (only two shown) of short axial length, say 2 inches, are respectively carried by brackets 61 that are vertically adjustable on the crossbar assembly 51 by means of square headed nuts 62. The supporting roller 56 rests upon these adjusting rollers 59. It will be seen that the matrix 35 lies in a plane tangential to the cylinder 12.

In use, the appropriate matrix 35 on its matrix frame 350 is located in position on the moving frame and the subassembly 50 carrying a rotary cylinder 12 is then clamped in its position. Prior to the location of cylinder 12 on the collars 55, the adjusting rollers 59 are set so that the supporting roller 56 does not bow but will give the correct support to the rotary cylinder 12 throughout its axial length. The vertical position of the crossbar 51 is now adjusted by screws 53 if necessary. The axial location of the cylinder 12 checked by comparing a datum mark on the matrix with a mark on the cylinder 12. The vertical height of crossmember 38 is now adjusted by the screws 39. The screws 45 are unwound so that the squeegee 43 can float to the correct height. The optimum loading of the squeegee 43 can be obtained by adding or removing weights from the trough 46.

Blocking medium is deposited upon the matrix 35 in an amount which is quantitatively exact so that it enables the rotary cylinder to be engraved and the engravings to be opaque. The moving frame and the matrix is now drawn forwardly by the motor 24 by means of the cord 27. The movement of the matrix 35 will, by friction, cause the rotary cylinder 12 to rotate and, at the same time, the blocking medium will pass through the positive matrix to produce a negative of great accuracy on the surface ofthe rotary cylinder 12.

The adjustments above described can be carried out with considerable accuracy, fineness and speed and the transfer operation can take place quite quickly, i.e. within a few minutes. The flat screen or matrix 35 can be recovered and retained for future use after each operation. It will be noted that the supporting roller 56 supports not only the rotary cylinder 12 but also the squeegee 43, so that the matrix does not have to carry the weight of the squeegee 43 and weight box 46. Also as the squeegee 43 is weighted along its length the tendency of the squeegee 43 to bow is minimized.

When preparing rotary screen cylinders for Duplex machines in which the fabric is printed on both sides and in which the reverse side of the fabric is printed with a mirror image of the pattern on the obverse side, the frame 35a and with it the matrix 35 can be inverted for preparing the rotary cylinder for printing upon the reverse side. In this case, packing blocks may have to be used to bring the matrix 35 up to the correct height in the machine.

The invention is not limited to the precise constructional details hereinbefore described and illustrated in the drawings and, for example, a rotatable squeegee roller may be used and/or other means of adjusting the heights of the various parts can be incorporated. f a rotatable squeegee 15 used, the

weight box may be supported thereabove with rollers, similar to rollers 59, resting on the squeegee. If desired an apparatus may be used whereby the matrix is held stationary and a rotary cylinder subassembly and squeegee moved horizontally along the matrix 35.

lclaim:

1. Apparatus for engraving a two-ply rotary screen cylinder with the negative of a pattern to be printed on textiles or the like, comprising means for mounting the rotary screen cylinder for rotation; means for mounting a flat screen matrix, carrying a positive engraving of said pattern, for movement tangentially to said cylinder and so as to rotate said cylinder; means for applying nipping pressure to the matrix and cylinder at the position at which they interengage; means for preadjusting said nipping pressure for causing a blocking medium applied to said matrix to be filled through the matrix and into the interstices of the cylinder, when the matrix is moved and the cylinder rotated, said means for applying nipping pressure comprising squeegee means engaging said matrix and an internal supporting roller located within said cylinder with the axes of said squeegee, said supporting roller and said cylinder being contained in a single plane; and adjusting roller means engaging with said supporting roller, said adjusting rollers being mounted within said cylinder for adjustable movement with said supporting roller in said single plane to adjust the nipping pressure derived from said supporting roller.

2. Apparatus as claimed in claim 1, wherein the squeegee means comprises a roller mounted for rotation.

3. Apparatus as claimed in claim 1, wherein said adjusting roller means comprises a plurality of rollers mounted for movement in said plane by screw threaded means,

4. Apparatus as claimed in claim 1, wherein loading means are provided to adjust the nipping pressure derived from said squeegee means.

5. Apparatus as claimed in claim 4, wherein the loading means comprises a receptacle for weights, said receptacle being mounted on said squeegee means said squeegee means being mounted for free-floating movement. 

1. Apparatus for engraving a two-ply rotary screen cylinder with the negative of a pattern to be printed on textiles or the like, comprising means for mounting the rotary screen cylinder for rotation; means for mounting a flat screen matrix, carrying a positive engraving of said pattern, for movement tangentially to said cylinder and so as to rotate said cylinder; means for applying nipping pressure to the matrix and cylinder at the position at which they interengage; means for preadjusting said nipping pressure for causing a blocking medium applied to said matrix to be filled through the matrix and into the interstices of the cylinder, when the matrix is moved and the cylinder rotated, said means for applying nipping pressure comprising squeegee means engaging said matrix and an internal supporting roller located within said cylinder with the axes of said squeegee, said supporting roller and said cylinder being contained in a single plane; and adjusting roller means engaging with said supporting roller, said adjusting rollers being mounted within said cylinder for adjustable movement with said supporting roller in said single plane to adjust the nipping pressure derived from said supporting roller.
 2. Apparatus as claimed in claim 1, wherein the squeegee means comprises a roller mounted for rotation.
 3. Apparatus as claimed in claim 1, wherein said adjusting roller means comprises a plurality of rollers mounted for movement in said plane by screw threaded means.
 4. Apparatus as claimed in claim 1, wherein loading means are provided to adjust the nipping pressure derived from said squeegee means.
 5. Apparatus as claimed in claim 4, wherein the loading means comprises a receptacle for weights, said receptacle being mounted on said squeegee means said squeegee means being mounted for free-floating movement. 